On 13 March 2017 at 14:28, <macpo...@parvis.nl> wrote: > my son needs for his music studies a python development environment 2.7.13 > plus the actual 3.x. > his imac is on osx 10.11 el capitan. > > so i installed from macports python 27 and 33, ipython, selects:
You mean Python 3.6? > questions: > - should i install ipython in this virtualenv > - if so, how (macports or not)? > > questions: > - does virtuelenv36 uses 2.7 dus to port --select? I don't understand this question. > - if so, how should i have done it? > > the big question: please explain to me the relation between macports > python/ipython/pip/virtualenv and how i should use it? when & how macports, > when & how not, why??? I'm not able to answer all of your questions, but you probably want to run sudo port select --set python2 python27 sudo port select --set python3 python36 sudo port select --set python python27 so that python, python2 and python3 will launch the desired version of Python (you can change the versions according to your needs), otherwise "python" will launch the system python. Generally I would say that if python packages from MacPorts satisfy your needs, it's probably better to stick with Python shipped by MacPorts and not use virtualenv at all (and use "sudo port install py27-whatever" rather than "pip-2.7 install whatever" or "pip install whatever"). Virtualenv is particularly important when using an "ancient distribution". (A lot of things become "ancient" pretty soon. Even the latest stable linux distribution might provide packages that are a few years old due to their strict release policies, while you might want to use either the bleeding edge version of a package (maybe because you filed a bug report that's blocking your work and they fixed the error, but didn't even provide a new release yet) or because the software you want to use no longer works with the latest package and you need an older one. Your son might get instructions telling him to run "virtualenv ... && pip install foo bar whatever". When using MacPorts, those commands should be slightly altered (you would want to find the suitable package), but in most cases the result should be perfectly fine. Only if some problems arise that cannot be addressed by MacPorts (or if the person doesn't know how to adapt the installation commands and doesn't want to bother), then it makes sense to use virtualenv. If some packages are missing, you could also request them. Mojca